Flash-powder.



UNITED STATES PATENT onnion JOHN I. CRABTREE', OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

' FLASH-POWDER.

No Drawing.

' To all whom it may concern:

Be it known that I, J oHNI. CILABTREE, a resident of Rochester, in the county of Monroe and State of New York, have invented new and useful Improvements in Flash- Powders, of which the following is a specification.

This invention relates to combustible substances, such as flash powders, that are used to furnish light in photography and other arts. One object of my invention is to pro- .vide a flash powder for illuminating purtests as the light from nitrogen tungsten.

lamps, while at the same time the powder possesses all other indispensable characteristics, viz., high actinic value of fiash, rapid and reliable speed of combustion, minimum 4 noise, minimum smoke, and practical immunity to premature ignitlon by friction and percussion. The powder is intended to be used not only in place of nitrogen tungsten lamps, where the latter are not available,

or to assist the latter where modified lightings and shorter exposures are desired,but also as an illuminant for photographing with color-sensitive plates and in general wherever an ordinary powder is used.

Flash light illumination is commonly carried out in two ways, (a) by burning metals in free oxygen as in a blow lamp, and (b) by burning metals along with modifying agents when mixed withsubstances contain ing combined oxygen, said agents modifying indispensable characteristics of the of the latter type.

ferent "combustible metals with various kinds of oxidizing and modifying agents, but extensive testing of these proposed mix- Specification of Letters Patent.

Patented Sept. 11, 1917.

Application filed December 11, 1916. Serial No. 136,384.

tures has shown that they are deficient in certain respects. Either they do not furmsh suflicient red light rays, or they lack some of the other essentials, producing, for instance, excessive smoke or a loud explosion, or costing too much for raw materials. My invention is intended to obviate these disadvantages and to provide a flash powder composition possessing all the properties that are considered necessary for photo graphic purposes.

One illustrative embodiment of this invention includes the following ingredients, which may be mixed in the proportions indicated as parts by weight:

Sodium oxalate 4 parts Red phosphorus 3. 5 Magnesium 5 Aluminum 10 l Strontium nitrate (crystal) 40 It is best that the ingredients be dry, free from lumps, and powdered to pass through a fine sieve. Furthermore, the redphosphorus should have been freed from yellow phosphorus, as by washing with caustic alkali. 'For homogeneity, the ingredients should preferably be mixed in the order givenin the formula, the oxalate and red phosphorus being first stirred together,

then the metals added, and finally the strontium nitrate shaken in.

While I have described the preferred embodiment of my invention, many variations falling within the scope of the appended claims will occur to those skilled in this art. For example, the red light in the flash may be slightly adjusted by varying the sodium oxalate or by partial substitution of the strontium nitrate, or other oxygen yielding salt of strontium, by barium nitrate. Where speed or comparative freedom from smoke is not particularly needed, the phosphorus may be wholly or partly replaced by red antimony sulfid or thesodium oxalate may be wholly or, partly replaced by sodium benzoate, naphthalene, or sodiumtungstate. The sodium oxalate, or one of its equivalents, h asbeen found necessary, to make the light from the'flash give, for practical purposes, the same spectroscopic results as the light from nitrogen tungsten lamps. It also adds to the ease or smoothness of burning of the powder and accomplishes these re sults without impairing the other characteristic essential. to a commercial flash powder. It may be noted that phosphorus and antimony sulfid are examples of easy burning substances which facilitate ignition and completecombustion In cases where speed is not required, as, for instance, still life subjects, a modification of my invention may be:

.Sodium oxalate 5 parts Bed phosphorus 2. 5 Aluminum 15 Strontium nitrate 40 This mixture is relatively slow but highly actinic and possesses the desired spectrum.

From the above formulae it is. evident thataluminum and mixtures of aluminum with magnesium act equivalently in these powders, so far as spectroscopic results areconcerned, the essential fact being that a combustible metal of high actinic value is mixed with my oxidizing and modifyinijgents.

' powders in this way in two parts renders- If the powder is made up to future use or to be transported, the .stron tium nitrate of. one charge should be inclosed in one package or compartment and the mixture of the other ingredients of that charge inclosed in a separate package or compartment; Thecontents of these tw o complementary packages are shaken together just prior to use. Putting up the them immune to premature ignition by friction or percussion.

The powder may be used in any customary Way, being laid, for example, in piles or trains, in open apparatus or in flash bags or flash cabinets, and preferably ignited electricallyor by flame. Ten grams of the powder ignited in a flash bag have been found suflicient, owing to its high actinic qualities, for taking a color portrait with a lens aperture of f. 6, though, of course, the amount will vary somewhat with other factors.

If powder of the characteristics set forth in the first formula above given is used, the effective duration of the flash averages about 1/20 of a second, a speed which is sufficient portraiture.

kept for.

to avoid defective photographs due to blinking and movement of nervous subjects in reaction, which takes place when the-powder is burned, determines the duration of the flash and can be varied byv changing the relative proportions of magnesium and aluminum, or by altering. the degree of fine- Even when burned in relaness of themetals, or by both varying the proportions and fineness of the metals. For example, the greater the proportion of magnesium or .the finer its state of subdivision the shorter will be the duration of the flash. Hence, a'very useful and exact adjustment -,of the speed of my powder to the requirements imposed by the particular circumstances, under which it is to be used, may be easily made.

I claim:

1. A flash powder comprisingcombustible metal of high actinic value, phosphorus, an

alkali earth metal nitrate, and a sodium salt, the efl ect of which on the flash is substantially like that-of sodium oxalate.

2. A flash powder mixture of sodium oxaactinic value, and an alkali-earth metal nitrate.

vlate,-phosphorus, combustible metal of high 3. A flash powdermixture of sodium oxa late, phosphorus, combustible metal of high 1 actinicvalue, and strontium nitrate. p

4:. A flash powder comprising sodium oxalate, red phosphorus, magnesium, aluminum" and strontium nitrate.

5. A flash powder composed substantially of strontium nitrate 40 parts, sodium oxalate 4 parts, red phosphorus 3.5 parts, magnesium 5 parts and aluminum 10 parts.

' JOHN I. CRABTREE.

Witnesses:

G. 0.: CooKE, R. L. STINCHFIELD. 

